With reference to the drawing, explanation will be made on a conventional lamp annealing apparatus or lamp annealer. The conventional lamp annealer comprises, as shown in a sectional view of FIG. 6, a chamber 1 made of quartz for annealing a wafer 4 held or loaded therein, a lamp 2 which is disposed over the chamber 1 and which generates infrared radiation, a pyrometer 3 which is disposed under the chamber 1 and which measures a temperature of the wafer 4 heated by the lamp 2, and a support member 5 on which the wafer 4 is held in the chamber 1.
The conventional lamp annealer is a single wafer processing apparatus which performs wafer processing one by one. In this apparatus, to perform anneal processing, the wafer 4 is at first held or loaded on the support member 5 in the chamber 1. Then, a voltage is applied to the lamp 2, and the lamp generates infrared radiation. The generated infrared transmits through the upper wall of the chamber 1 and is radiated on the wafer 4. The wafer radiated by the infrared is heated, and the light emitted from the heated wafer 4 transmits through the lower wall of the chamber 1. The light thus transmitted through the lower wall of the chamber 1 is measured by the pyrometer 3 to generate indication of a temperature. By using the indication of the temperature, the heating temperature of the wafer is adjusted to an appropriate value. Such heating process is performed on a wafer one by one.
In the conventional lamp annealer shown in FIG. 2 and described above, when the wafer to become a product is processed by heat treatment, emission of impurities, particles, molecules and the like, or outgassing, (hereinafter referred to as out-diffusion) occurs from inside of the wafer or from thin film formed on the wafer and so on. As these heat treatment is repeated a number of times, inside wall of the chamber is gradually contaminated due to the out-diffusion. Therefore, the light which is emitted from the heated wafer and which is to reach the pyrometer 3 is partially reflected or absorbed by the contaminated inner wall of the chamber 1 just above the pyrometer 3. As a result, quantity of light transmitting through the lower wall of the chamber 1 and arriving at the pyrometer 3 varies, and there was a deviation between an actual temperature of the wafer 4 and a temperature measured by the pyrometer 3. Therefore, it was impossible to appropriately control anneal temperature of the wafer.
In order to control the variation or dispersion of the anneal temperature of the wafer, Japanese patent laid-open publication No. 2-132824 proposes a lamp annealer. In the lamp annealer, a monitor wafer having the same characteristic in temperature rise and temperature fall as that of a silicon wafer to be processed is disposed near the silicon wafer to be processed, and temperature of the monitor wafer is monitored by a radiation thermometer to perform temperature control.
However, in the lamp annealer disclosed in Japanese patent laid-open publication No. 2-132824, since the monitor wafer and the wafer to be processed are both disposed in the same chamber, divergence between the actual temperature and the measured temperature of the wafer caused by the contamination of the inner wall of the chamber cannot be properly removed, and it is impossible to perform appropriate and reproducible heat treatment.
In order to solve the problems of the conventional technique mentioned above, present invention aims to improve reproducibility of the anneal temperature of a lamp annealer, and to stabilize characteristics of a product wafer.